1. Field of the Invention
The present invention relates to a squeeze roller elevating apparatus of a liquid electrophotographic printer.
2. Description of the Related Art
In a liquid electrophotographic printer, a developing unit for developing an electrostatic latent image formed on a photoreceptor belt is provided. The developing unit, as shown in FIG. 1, includes a developing roller 13 for developing an electrostatic latent image by supplying a developer 1 which is a mixture of powdered toner and a liquid carrier to the photoreceptor belt, and a squeeze roller 11 for removing excess developer from the photoreceptor belt 10.
The squeeze roller 11 presses the photoreceptor belt 10 against a backup roller 12 in a print mode to remove the extra developer. In a stand-by mode after printing, the squeeze roller 11 is separated from the photoreceptor belt 10 and a pressing force is removed. There is a "drip-line" removing mode for removing a "drip-line" between the print mode and the stand-by mode. A "drip-line" is generated when the developer remains in a portion where the squeeze roller 11 and the photoreceptor belt 10 closely contact one another during printing. In the drip-line removing mode, a pressing force of the squeeze roller 11 to the photoreceptor belt 10 is slightly reduced and the squeeze roller 11 is rotated opposite the circulation direction of the photoreceptor belt 10 so that the remaining developer is detached to the bottom.
For the above operation, a liquid electrophotographic printer is provided with a squeeze roller elevating apparatus so that the squeeze roller 11 is separated from the photoreceptor belt 10, in the stand-by mode, and is elevated and pressed to the photoreceptor belt 10 in the print mode. Also, in the "drip-line" removing mode, a pressing force can be reduced.
The structure of a conventional squeeze roller elevating apparatus is shown in FIG. 2. A squeeze frame 20 having a squeeze roller 11 is installed at a main frame 40 to be capable of elevating. The squeeze frame 20 is elevated by a cam 22 rotated by a driving motor (not shown) and thus the squeeze roller 11 can be elevated. Reference numeral 30 refers to a belt frame which supports the photoreceptor belt 10 so as to not deviate from a regular circulation path.
In the squeeze roller elevating apparatus having the above structure, when the squeeze roller 11 is lifted to press the photoreceptor belt against the backup roller 12, a repulsive or reactionary force to the pressing force is directly transferred to the main frame 40, which becomes a problem. That is, since the reactionary force to the force pressing the photoreceptor belt 10 is applied to the main frame 40 supporting the squeeze frame 20, a distortion transformation can be generated to the main frame 40 when printing continues for a long time. Thus, a squeeze roller elevating apparatus which can best prevent the transfer of such a reactionary force applied to the main frame 40 is required.